composite is sd, and video out is less intensive than stream in.
you still would need the component to connect to the camera or a device that will stream over wifi, it's not cost effective, why would someone make that device and make the app for the ipad, for like 20 app buyers that won't pay that much for the app nor the device that will stream.
if the canons can send low bitrate, compatible h.264 over wifi, that will still cost a lot for the adapter thing, and won't be hd monitoring. that would be an app only solution considering you will pay for the adapter which costs too much. and still the app would only sell for 20 or less people.
20 people or less?
I think more than 20 people alone on these very forums would buy an Ipad alone if this was possible ( including me ). Never underestimate yourself, DSLRs are very popular right now so is the Ipad. With the right marketing they can sell hand in hand, who knows if it will happen but I strongly disagree with you on thinking that no one will buy it.